The instant invention relates to electrophotocopying machines in general, and more particularly to a camming system for moving a developer unit into and out of developing engagement with a photoconductive surface.
In electrophotocopying, as typified by xerography, it is usual to form an electrostatic image on a photoconductive surface conforming to the original document being reproduced. This image is then developed or made visible by the application of an electrostatically attractable material which is deposited in conformity with the latent electrostatic image.
In xerographic development systems, especially those employing single component developer material, a uniform development zone between the developer unit applicator roller and the photoreceptor is essential to consistent latent image development. Because the photoreceptor experiences certain deviations from its nominal location due to mechanical tolerances of its support member, it becomes necessary to either rotate the developer unit about a point or translate the unit through a plane such that the developer unit will follow the mechanical runout of the photoreceptor. A further complication appears in some systems, whereby extended interfacing of the developer unit with the photoreceptor under certain conditions (e.g. overnight) results in migration onto the surface of the photoreceptor. Upon machine activation, this effect allows a quantity of developer material on the photoreceptor surface to be transported to the roll transfer station (if utilized) and the photoreceptor cleaning station. After a number of machine cycles have been completed, the imposition of this additional developer material may contribute to premature failure of the interfacing system. To alleviate this condition, a mechanism must be added to engage and withdraw the developer unit from the photoreceptor. A typical device for moving the developer unit into and out of developing engagement with the photoreceptor is disclosed in U.S. Pat. No. 3,743,407 issued July 3, 1973.
The instant invention achieves the same result of moving the developer unit into and out of developing engagement with the photoreceptor as the prior art devices, but it does so without the need for any engagement springs, spring securing pins or two-way solenoids to move the developer unit.